A multi-chamber system is known as an apparatus for performing vacuum processing that is one of semiconductor device manufacturing processes while ensuring a high throughput. In this system, a plurality of vacuum processing chambers are connected to a common vacuum transfer chamber through respective gate valves, and a substrate is transferred from an atmospheric pressure or an inert gas atmosphere of an ordinary pressure to the common vacuum transfer chamber through a load-lock chamber and then transferred to one of the vacuum processing chambers by a transfer unit in the vacuum transfer chamber. The vacuum processing may include film formation, dry etching, annealing, and the like.
Conventionally, when a semiconductor wafer (hereinafter, referred to as “wafer”) is transferred between the vacuum transfer chamber and the vacuum processing chamber, an atmosphere of the vacuum processing chamber is prevented from flowing into the vacuum transfer chamber by opening/closing the gate valve in a state where a pressure in the vacuum transfer chamber is maintained at a level slightly higher than that in the vacuum processing chamber. Depending on a type of processing of the wafer or a structure of the vacuum processing chamber, reaction by-products generated during the processing may be adhered and deposited to an inner surface of the vacuum processing chamber, especially to a vicinity of the gate valve. Accordingly, when the atmosphere inert gas in the vacuum transfer chamber flows into the vacuum processing chamber by opening/closing the gate valve, the reaction by-products may be peeled off and adhered as particles to a surface of the wafer being transferred.
Japanese Patent Application Publication No. 2009-64873 discloses a technique for suppressing adhesion of particles to a surface of a wafer by opening/closing a gate valve after setting a flow rate of a gas in a vacuum processing chamber twice or more than that in a vacuum transfer chamber in a state where a pressure in the vacuum transfer chamber is set to be higher than a pressure in the vacuum processing chamber. However, the flow rate of the gas in the vacuum transfer chamber may be suddenly increased and, thus, the particles may be peeled off. In addition, when the flow rate of the gas in the vacuum processing chamber is set to be greater than that in the vacuum transfer chamber, the particles may scatter into the vacuum transfer chamber.